1. Field of the Invention
The present invention relates generally to film feed mechanism for cameras, and more particularly, to film feed mechanisms for cameras where the take-up shaft and the film take-up spool are spaced apart from each other.
2. Description of the Prior Art
In a camera, the preferred arrangement is to have the film take-up spool disposed in the vicinity of the take-up shaft. In a camera arrangement where the take-up shaft and the film take-up spool are spaced apart from each other, maximum ease of operation requires a complicated transmission mechanism within the body of the camera, particularly in the case where an unidirectional rotating take-up shaft is employed.
Japanese Patent Application No. 52-69,725 is directed to a transmission mechanism where a unidirectional rotating take-up shaft is employed, and this Japanese Patent Application is incorporated by reference into the present application. Briefly stated, in Japanese Patent Application No. 52-69,725, the rotational movement of a film feed controlled disc, which is derived from the take-up shaft, is converted into reciprocating movement of a bell crank by the use of a link. The reciprocating movement, in turn, is converted into intermittent unidirectional rotation of a take-up spool by the use of a one-way clutch. However, the intermittent unidirection rotation that is produced causes the level of torque applied to the film during the take-up operation to be very uneven.
The film feeding mechanism disclosed in Japanese Patent Application No. 52-69,725 is shown in FIG. 1. To facilitate the explanation, the film feed stopping mechanism, the take-up operation interrupting mechanism, and the mirror and shutter setting mechanism have been omitted. Referring to FIG. 1, a gear 1 is coupled to the take-up shaft (not shown). The take-up shaft rotates in only one direction, and causes gear 1 to rotate only in the clockwise direction, as indicated by the associated arrow. Gear 1 meshes with a setting gear 2, which meshes with a gear 3. Thus, gear 3 also rotates only in the clockwise direction, as indicated by the associated arrow. Mounted on gear 3 is a film feed control disc 4. A link 6 is coupled at a first end to the film feed control disc 4 by a shaft 5, and at a second end to a bell crank 8 by a shaft 7. Bell crank 8 is mounted for rotation on a shaft 8a. Thus, the clockwise rotation of the film feed control disc 4 causes link 6 to move reciprocally, which causes bell crank 8 to move reciprocally, as indicated by the associated arrow.
A driving gear 11 is also mounted for rotation on shaft 8a. A pawl 9 coupled by a shaft 8b to bell crank 8 is urged by a spring 10 against the teeth of driving gear 11. Because of the shape of the teeth of driving gear 11 and the orientation of pawl 9, pawl 9 only engages the teeth of driving gear 11 when bell crank 8 is being moved reciprocally to the right. Thus, bell crank 8, pawl 9, spring 10 and driving gear 11 constitute a one-way clutch which causes gear 11 to be rotated clockwise when bell crank 8 is moved reciprocally to the right.
A gear 12 is also mounted for rotation by shaft 8a and is rigidly secured to driving gear 11. Gear 12 rotationally connected to a spool gear 16 by way of a series of gears 13, 14 and 15. In addition, a spring 17 acts to prevent counterclockwise rotation of gear 12. Thus, when gear 12 rotates in an intermittent clockwise fashion, spool gear 16, associated with the film take-up spool, correspondingly rotates in an intermittent counterclockwise fashion.
As stated above, because gear 12 is rotated only when the bell crank 8 is being moved reciprocally to the right, the level of torque applied via spool gear 16 to the film during the take-up operation is very uneven.